In the manufacture of large, high speed computers, it is necessary to cool the electronic components and devices which form a portion of the processor to a very low operating temperature, and to operate these components in a vacuum. In order to cool the components, it is necessary to mount the components in contact with a thermally conductive structure which then is cooled to a very low temperature. This low temperature cooling may be accomplished by cryogenic cooling unit, which utilizes a low temperature gas or liquid, such as gaseous Helium, at approximately 77 degrees Kelvin (K.) as the cooling vehicle circulated in the cryogenic cooling unit which is placed underneath and in contact with the cold plate of a vacuum container. In order to prevent problems with moisture in the air condensing as the electronics are cooled to such a low temperature, a vacuum is formed surrounding the electronic elements within a sealed vacuum container.
Sealed vacuum containers are well known. However, it has been a problem to maintain the vacuum when a path of electrical communication must pass through the walls and into the evacuated region of the container. Attempts have been made to form a container which has a plurality of apertures in its periphery and to form a seal around a rigid circuit board. The circuit board is then connected to a flexible cable on both ends. The sealing is accomplished by a rigid potting compound such as epoxy as it passes through the wall aperture formed in the wall of the container. An example of such a structure is found in Research Disclosure, February 1988, page 92.
Efforts to provide seals at the container walls which allow conductors or cabling to pass through the walls has proven to be unreliable, since movement of the sealing and conducting structure may break the seal and destroy the vacuum.
Further, the use of connectors, which may be part of the sealing arrangement, to seal the apertures in the cooling unit wall require precision manufacturing and greatly increase the cost of such a cryogenically cooled module.
Electrical communication from the exterior to the interior of a chamber may be accomplished as shown in U.S. Pat. No. 4,161,655 to Cotic et al.; a circuit board is trapped between sealing rings and gaskets formed of neoprene to seal the interior chamber. The neoprene ring gaskets are mounted in and retained in a metal gasket carrier or ring on each side of a printed circuit board. The circuit board of Cotic et al.; is not molded into the gasket rings of neoprene but relies strictly upon the surface of the neoprene ring being compressed against the surface of the circuit board sufficient to create an adequate seal for the containment of the gas contained in the chamber.
Another technique for sealing a container, within which electronic elements or circuits are contained, involves the use of sealing glass such as that disclosed in U.S. Pat. No. 4,931,854 to Yonemasu et al.; an integrated circuit package is sealed by the use of sealing glass and the fusing of that glass to form the seal between the base and cover and surrounding the leads leading to the integrated circuit. The cooling of the assembly to very low temperatures may crack the glass seal if the package shrinks at a different rate than the glass.
Resins such as epoxy, silicone, polyimide and the like may be used to encapsulate an electronic device and to seal that device from the surrounding atmosphere. This approach is shown in U.S. Pat. No. 4,814,943 to Okuaki, where there is no effort to either pressurize or evacuate the container.